New Mecyclothorax spp. (Coleoptera, Carabidae, Moriomorphini) define Mont Mauru, eastern Tahiti Nui, as a distinct area of endemism

Abstract Seven species of Mecyclothorax Sharp precinctive to Mont Mauru, Tahiti, Society Islands are newly described: Mecyclothorax tutei sp. n., Mecyclothorax tihotii sp. n., Mecyclothorax putaputa sp. n., Mecyclothorax toretore sp. n., Mecyclothorax anaana sp. n., Mecyclothorax pirihao sp. n., and Mecyclothorax poro sp. n. These seven constitute the first representative Mecyclothorax species recorded from Mauru, and their geographic restriction to this isolated massif defines it as a distinct area of endemism along the highly dissected eastern versant of the Tahiti Nui volcano. Each of the new species has a closest relative on another massif of Tahiti Nui, supporting speciation associated with vicariance caused by extensive erosional valley formation, especially the development of Papenoo Valley. Comparison of the known elevational distributions of the new discoveries on Mont Mauru to the elevational diversity profile of the comparatively well-sampled Mont Marau, northwest Tahiti Nui, suggests that numerous Mecyclothorax species remain to be discovered in higher-elevation habitats of Mont Mauru.

The island of Tahiti is remarkably dissected.The two volcanoes that comprise Tahiti-Tahiti Nui and Tahiti Iti-are estimated to have formed 1.75 and 1.0 Myr ago (Craig et al. 2001), and both have undergone extensive erosion leading to deep, broad valleys separating narrow ridgelike mountains with extremely steep slopes.At the center of Tahiti Nui, Mont Orohena stands 2.241 km tall less than 5 km from the 169 m elevation floor of Papenoo Valley.To Papenoo Valley's east lie a series of isolated massifs that comprise the dissected, windward and eastern versant of Tahiti Nui volcano.To its west range a set of interconnected ridge systems; Marau, Aorai, and Pihaaiateta (Fig. 1), the latter culminating in Mont Orohena.This paper presents the first descriptions of Mecyclothorax carabid beetles precinctive to one of the isolated eastern massifs; Mont Mauru (Fig. 1).All of the species discovered on Mauru are new to science.The novel aspects of Mauru's beetle fauna stem from the historical restriction of all prior carabid beetle sampling in Tahiti Nui to the interconnected western ridges.Perrault (1978aPerrault ( , 1978bPerrault ( , 1984Perrault ( , 1986Perrault ( , 1987Perrault ( , 1988Perrault ( , 1989) ) collected extensively on Marau, Aorai, and Pihaaiateta, as well as in the mountains of Teatara, Presqu'île de Taiarapu, Tahiti Iti (Fig. 1).He found that even among the interconnected ridges of western Tahiti Nui, most species are restricted to a single ridge system (Perrault 1992).Given the extreme geographic isolation of Mont Mauru vis à vis the western sites sampled by Perrault, it should come as little surprise that Mont Mauru houses a fauna completely distinct from that of the western mountains.Nonetheless, sampling accomplished to date on Mont Mauru remains very limited, suggesting that our biological knowledge of this massif's Mecyclothorax diversity is dramatically incomplete.To make an initial estimate of the level of our ignorance, the elevational distributions of Mecyclothorax beetle species on Mauru are compared to those observed on Mont Marau, the best sampled and therefore apparently most diverse Tahitian mountain.By this estimate, somewhere between ¼ to ½ of the Mecyclothorax fauna of Mauru has been discovered, lending support for further biological survey activities on this massif.

Taxonomic material
This study is based on 41 Mecyclothorax specimens-40 adults plus 1 larva-collected on Mont Mauru during September, 2006.Diagnoses of all new species were developed through comparison with type specimens of Tahitian Mecyclothorax species described by Perrault (1978a et seq.), as well as specimens representing 35 described species plus 20 additional new species, to be described subsequently, that were collected elsewhere in Tahiti during September, 2006.Paratype specimens of Perrault species were borrowed from the Naturhistorisches Museum, Basel (NHMB) and the Muséum national d'Histoire naturelle, Paris (MNHN).Specimens representing all Mecyclothoarx species in the Georges G. Perrault collection of Tahitian Carabidae (MNHN) were photographed, 24-26 August 2006, at which time structural, setational, and microsculptural characters were noted for all described species held at Paris.These include specimens for species described by Britton (1938).The sum of these comparisons plus associated notes, along with Perrault's (1992) hypotheses of phylogenetic affinity, were used to formulate hypotheses of sister-group relationships for the new species described below.
Primary type specimens and associated allotypic paratypes of the new species, where available, are deposited in the MNHN and incorporated into the

Laboratory techniques
This paper follows directly the laboratory protocols and anatonomical terminology presented in Liebherr (2009Liebherr ( , 2011)).Those papers may be consulted for explanations of the terminology used below.

Descriptive conventions
Various ratios of length and width are used to describe shapes of the head, pronotum and elytra.For the head these include the ocular ratio, the width across the outer surface of the compound eyes divided by the minimum width of the frons between the eyes, and the ocular lobe ratio, the diameter of the eye measured from above, divided by the distance from the front margin of the eye to the juncture of the ocular lobe and gena, measured from the same vantage point.Prothoracic dimensions presented as ratios include: MPW, maximum pronotal width; BPW, basal pronotal width, measured between the hind angles; APW, apical pronotal width measured between the two most anterior points at the pronotal front angles; and PL, pronotal length measured along the midline.Elytral dimensions include MEW, or maximum elytral width, and HuW, humeral width, measured between the most anteriorly positioned points, i.e. the humeral angles.Standardized body length comprises the sum of three values: 1, the length of the head from labral anterior margin to cervical ridge, the position of the ridge estimated from its lateral reaches when hidden medially under the pronotal margin; 2, median pronotal length; and 3, elytral length, distance from base of scutellum, where the surface dips ventrally, to apex of the longer elytron, measured along the suture.
When more than one individual was used to represent a ratio or range of ratios, the quantified number is followed by "(n = X)", with X representing the number of individuals measured to make up the ratios.A maximum of five individuals were so measured for any species, with the largest individual, the smallest individual, and representatives of both sexes included in the sample of five.By this method the most disparate range of ratios was sought.The ratios are used only for descriptive purposes and are not statistically evaluated.

Collecting localities
Entomological sampling of Mont Mauru, eastern Tahiti Nui, was facilitated by the private access road to the hydroelectric facilities of Électricité de Tahiti.The lowest elevation collecting site was along a northern tributary branch of the Faatautia River at a 30 m length of uncollapsed lava tube housing a highly variable stream (Fig. 2A).The lava tube was traversable at low water (18 September), with a small waterfall at its lower mouth bordered by a flat rocky terrace.At higher water (5 September), the flow covered the lava tube floor, flowing as high as the upper limit of the scoured rockface to the right of the terrace (Fig. 2A).
The hydroelectric facility transmits its electicity to Papeete by means of high tension lines strung on metal pylons, with four pylons traversing the southwestern portion of Mont Mauru from 850 m to 1060 m elevation.Access to habitats near the pylons is facilitated by the remnants of the original construction road, although erosion has eliminated portions of this track making it impassable for vehicles above 650 m elevation.Fern banks line old roadcuts (Fig. 2B), and open mesic forest with limited mossmats on tree trunks is accessible from the trail.The fourth pylon at 1060 m elevation stands near the margin of low-stature wet montane forest, dominated by Weinmannia and Metrosideros trees that form an open canopy of stunted trees covered with thick mossmats (Fig. 2C).Abundant epiphytic growth occurs on older, decumbent nurse logs.This low wet forest was sampled up to 1110 m elevation, above which collecting was precluded by inclement weather.
Latitude and longitude readings were made at all collecting localities using a Garmin etrex® 12 channel GPS unit, with coordinates used to map the localities onto I.G.N. (1994).Distances between sites along elevational transects were then calculated and used to determine the elevational profiles of the collecting localities.Beetle distributions along elevational transects on Mont Mauru and Mont Marau were compared to obtain a comparative estimate of species distibutions relative to elevation.
Etymology.The species epithet honors Captain James Cook who named the Society Islands after the Royal Society, at whose behest he observed the 1769 transit of Venus from Tahiti.The epithet is his last name in Tahitian, Tute (Wahlroos 2002), treated as a latinized second declension noun in the genitive singular; tutei.
Distribution and habitat.The lone specimen of this species was found in tangles of living and dead fern fronds in low-stature wet montane Weinmannia and Metrosideros forest at 1080 m elevation.The beetle was collected from a beating sheet held under fronds that were sprayed with synthetic pyrethrin.The single specimen of M. toretore and a series of M. pirihao were also found using this method at this elevation.

M. altiusculus species group
Diagnosis.This species group comprises a disparate assemblage of taxa that Perrault (1988) suggested may need subdivision.The species treated below adheres to the original (Perrault 1986), less inclusive concept of the group, whereby the included taxa are assigned based on a pronotum that is basally constricted with straight to briefly sinuate basolateral margins and glabrous hind angles.
Variation.Although this species is characterized by the presence of two dorsal elytral setae, the two known specimens vary in this regard.The male holotype exhibits only an anterior seta on the left elytron, and only a posterior seta on the right.The female allotype has both anterior and posterior setae present on the left elytron, but only the anterior seta on the right side.
Male genitalia.Aedeagal median lobe narrow and straight basally, right lateral view (Fig. 5A), curved downward apicad articulatory projection of parameres, apex broadly rounded, a large ostial flap at apical margin of ostial opening (Fig. 5A); median lobe curved to the right apically in euventral view (Fig. 5B), the axis of apex nearly perpendicular to axis of median lobe base; internal sac with well-developed ventral microtrichial field but without distinct spicules; flagellar plate moderately large, length ⅓ distance from parameral articulation to distal surface of apex; parameres extended 0.82× distance from parameral articulation to distal surface of apex.
Female reproductive tract.Bursa copulatrix broad basally, narrowed to apical third that extends as a narrow projection (Fig. 6A); bursal membrane thin, unwrinkled under microslide cover slip; spermatheca broadest in apical half, length 0.2× length of spermathecal duct, duct joined to dorsal wall of bursa dorsad the basally broad common oviduct;  spermathecal gland with orbicular reservoir, the reservoir about ½ length of duct which enters at base of spermatheca; membranous ramus at base of basal gonocoxite of usual length for Mecyclothorax spp.(e.g., Liebherr 2011Liebherr , 2012)), extended about ⅓ length of basal coxite (Fig. 7A); basal gonocoxite 1 with 3 apical fringe setae, medial surfaces from dorsal to ventral with about 8 very small setae; apical gonocoxite 2 narrow, apex subacuminate, with 2 lateral ensiform setae, the basal seta shorter and narrower than apical seta, 1 dorsal ensiform seta, and 2 short apical nematiform setae in small pitlike depression.
Holotype male (MNHN) labeled: Etymology.Based on the extreme similarity of this species to M. ballioides, by which Georges Perrault honored Professor George E. Ball, the species epithet tihotii-Tahitian for George (Wahlroos 2002)-is used.The epithet treats Tihoti, George, as a latinized second declension noun in the genitive singular.
Distribution and habitat.The holotype was collected in a pyrethrin fog sample of moss-covered Metrosideros trunks (e.g., Fig. 2C) that served as nursery logs for Melicope plants.This specimen plus the holotype of M. putaputa comprised the entirety of carabid beetles from that sampled trunk.The female allotype was collected by beating Myrsine and mossy vegetation in the same area of low-stature forest, the allotype syntopic with two specimens of M. anaana.

M. viridis species group
Diagnosis.Member taxa of this species group are diagnosed by a pronotum with base narrower than maximal breadth near midlength, and lateral margins distinctly sinuate immediately anterad the projected, setose hind angles.The elytra are convex and ellipsoid (Fig. 3C).This is the sixth species described in the group.Of the others, two each are recorded from Mont Marau and Mont Aorai (Perrault 1986), and one is known from Mont Tohiea, Moorea (Liebherr 2012).Diagnosis.This species shares well-developed microsculpture on head, pronotum and elytra with M. castaneus Perrault, the sculpticells a mixture of isodiametric and transverse on frons, transverse on pronotal disc, and of dense transverse lines on the elytral intervals.The discal elytral striae are distinctly punctate in this species, with the punctures in the basal third of striae 1-4 expanding the breadth of the striae, a character shared with M. mapo Liebherr of Moorea.However M. mapo differs by transverse-mesh elytral microsculpture and obsolete microsculpture on head and pronotum.This species differs from both M. castaneus and M. mapo by the obtuse-rounded pronotal hind angles, versus right and sharp hind angles in those two species.Whereas the two type specimens of M. castaneus (Perrault, 1986) variably exhibit one or two dorsal elytral setae (one the more common condition), the two specimens of this new species plus those of M. mapo are uniformly bisetose; setal formula 2221.Beetles of this species exhibit standardized body length 4.3-4.5 mm versus 3.8-4.1 mm for M. castaneus.The type series of M. mapo includes individuals with body length ranging 3.8-4.4mm.
Female reproductive tract.The unique female holotype was not dissected, although the gonocoxae were exposed allowing their preliminary characterization (Fig. 8B).Basal gonocoxite 1 narrowed apically to narrow, scimitar-like apical gonocoxite 2; basal gonocoxite 1 with apical fringe of 4 setae; apical gonocoxite 2 narrow basally, curved, apex acuminate, with 2 lateral ensiform setae, the basal lateral seta much smaller than the apical seta, and 1 dorsal ensiform seta (visible through gonocoxite in ventral view); apical gonocoxite with 2 apical nematiform setae in pitlike depression.Initially, the female paratype was dissected, although the specimen apparently suffered trauma in the killing jar, as only the base of each basal gonocoxite 1 jaggedly remained attached to laterotergite IX.The internal reproductive tract was also damaged, however the following characters could be determined: bursa copulatrix ovoid with length twice breadth when compressed on microslide, apex with slight constriction defining an ill-defined apical lobe; spermatheca orbicular, spermathecal length about ¼ length of spermathecal duct; spermathecal gland entering base of spermatheca, the duct subequal in length to apical gland reservoir.
Holotype Etymology.The species epithet, putaputa, is Tahitian for punctured (Wahlroos 2002), signifying the distinctly punctate discal elytral striae.The epithet is to be treated at a noun in apposition.
Distribution and habitat.The two specimens of this species were found at 1060 and 1100 m elevation, in low-stature Weinmannia and Metrosideros forest.One specimen was collected in a pyrethrin fog sample from moss growing on a Metrosideros trunk, the second by beating vegetation along the margins of openings in the forest.M. tihotii and M. anaana were the two species found syntopically in these situations (Fig. 2C).

M. globosus species group
Diagnosis.Members of this group are characterized by the narrow pronotum with narrow lateral marginal depression, and the lateral pronotal margin elongately sinuate anterad the glabrous hind angle (Fig. 4).Perrault (1989)  Diagnosis.This species shares fully striate elytra and transversely-lined elytral microsculpture with M. fuscus Perrault.Both species are also characterized by presence of only the anterior dorsal elytral seta and only the apical elytral seta; setal formula 2111.However, this species differs by: 1, the very narrow elytra with subparallel lateral margins versus more ovoid elytra in M. fuscus; and 2, the laterally extended humeri resulting in a MEW/HuW ratio of 1.89 in this species, versus MEW/HuW = 1.97 for M. fuscus.The pronotal hind angles are also profoundly margined in this species (Fig. 4A), with the lateral and basal marginal beads defining a U-shaped pronotal laterobasal depression.Conversely, the hind angles are upraised but without a distinctly beaded margin in M. fuscus.Standardized body length is 4.2 mm for this species versus 4.0 mm for M. fuscus.
Female reproductive tract.-Theunique female holotype was not dissected, although the gonocoxae were exposed allowing their preliminary characterization (Fig. 8C).Basal gonocoxite 1 with angulate apical margin, the margin angled toward base along lateral half of apical gonocoxite 2; basal gonocoxite with apical fringe of 2 setae; apical gonocoxite 2 distinctly convergent in basal half of length, apical half more narrowly convergent to subacuminate tip, with 2 lateral ensiform setae and 1 dorsal ensiform seta that extends medially-and is thus visible in ventral view-and 2 apical nematiform setae.
Etymology.The Tahitian word toretore means striped, as in striped cloth (Wahlroos 2002).The word's use as the species epithet signifies the deep, distinct elytral striae, and is to be used as a noun in apposition.
Distribution and habitat.The lone specimen of this species was found in the highest, wettest rain forest sampled-1080-1100 m elevation-during a tropical rainstorm, the use of a hand-held pyrethrin fog canister over a beating sheet the sole collecting method of any utility under those conditions.That the beetle plus those of M. tutei and M. pirihao were found in dead fern tangles during this storm suggests that the beetles had moved into such tight quarters due to the rain.Neither M. tutei nor M. toretore were collected during drier conditions in this elevational band of forest even though extensive beating of vegetation had been undertaken over the course of three days.
Male genitalia.(n = 1).Aedeagal median lobe broad basally and narrowed in apical half to finely protruded apex with downturned tip (Fig. 5C); median lobe straight in euventral view; internal sac with broad melanic ventral microtrichial field but without spicules; flagellar plate large, length 0.46× distance from parameral articulation to distal surface of downturned tip; paramere extended 0.83× distance from parameral articulation to tip.
Female reproductive tract.(n = 1).Bursa copulatrix columnar, broadest near midlength, length 2.3× maximal breadth when compressed on microslide (Fig. 6B); bursal walls moderately thickened, wrinkled, and variably stained with Chlorazol Black; spermatheca obovate, broadest near apex, reservoir length about ¼ length of spermathecal duct that joins dorsal bursal wall dorsad bursal juncture with common oviduct; spermathecal gland with elongate reservoir, reservoir length subequal to spermathecal gland duct length; membranous ramus mesad basal gonocoxite 1 long, apex extended beyond midlength of basal gonocoxite (Fig. 7B); basal gonocoxite 1 with apical fringe of 3-4 setae-3 on left side, 3 plus 1 isolated apicolateral seta on right side-and only several small setae along medial surface; apical gonocoxite 2 broad basally, narrowed in apical half to subacuminate apex; apical gonocoxite with 2 subequal lateral ensiform setae that are situated on the ventral surface, 1 dorsal ensiform seta, and 2 apical nematiform setae.Etymology.The Tahitian word anaana means bright, shining, or brilliant (Wahlroos 2002), and is used to describe the glossy dorsal body surface of beetles of this species.As a Tahitian word the epithet is to be treated as a noun in apposition.
Male genitalia.(n = 2).Aedeagal median lobe evenly curved and of subequal diameter from basal bulb to ostial opening, apex with rounded dorsal projection at base, the downturned tip rounded to tightly rounded (Figs 5D, E); median lobe straight in euventral view; internal sac with broad ventral microtrichial field but without spicules; flagellar plate of moderate size, length 0.35× distance from parameral articulation to distal face of apex; parameres extended 0.83× distance from parameral articulation to apex.
Holotype male (MNHN) labeled: French Polynesia: Etymology.The Tahitian word pirihao, meaning narrow, constricted, or close (Wahlroos 2002), is used to signify the basally constricted pronotum characterizing this species.As Tahitian, the species epithet pirihao is to be used as a noun in apposition.
Distribution and habitat.This is the most commonly encountered, and most broadly distributed species within the elevational range so far sampled on Mauru, having been collected in habitats at 880-1110 m elevation.However, 20 of the 22 specimens were collected in association with ferns of either the genus Blechnum or Dicranopteris, and only 2 were associated with flowering plants; a mixed beating sample from Weinmannia, Myrsine, and Melicope.7. Mecyclothorax poro sp.n. urn:lsid:zoobank.org:act:5474B951-8E36-4480-B240-7CBF0EA7836Ehttp://species-id.net/wiki/Mecyclothorax_poroFig. 4D Diagnosis.This species shares with M. angulosus Perrault the distinctly constricted lateral pronotal margins anterad right, projected hind angles.Both species are also characterized by two supraorbital setae and two dorsal elytral setae, and therefore a setal formula of 2121.Both also display dense transverse-line elytral microsculpture loosely joined in a mesh, the microsculpture resulting in an aeneous reflection.The pronotal median base is more distinctly punctate in M. angulosus, and the cuticle between the punctures is covered with indistinct transverse microsculpture, versus the smooth areas between punctures observed in this new species (Fig. 4D).Elytral stria 6 is shallow and nearly smooth near the elytral midlength in this species, versus deeper and punctate-nearly as deep as striae 1-5-in M. angulosus.Also, elytral striae 2-6 are obsolete basally in this species, versus deep and continuously depressed to their juncture with the elytral basal groove in M. angulosus.Standardized body length in this species is 4.4 mm, larger than M. angulosus at 4.0 mm (n = 2; MNHN holotype male plus CUIC female).
Female reproductive tract.The unique female holotype was not dissected, nor were its external genitalia visible for examination.
Larva.One larval specimen was collected 18-ix-2006 by use of pyrethrin fog on a moss-covered boulder at the upper mouth of the lava tube, 725 m elevation.Complete description of the larva will be presented subsequently, but identification as Mecylothorax sp. is possible based on its intrinsic characters assessed within the context of the disharmonic carabid fauna of Tahiti.Using Emden (1942), the specimen keys to couplets 28 and 29 whereupon it violates the key, exhibiting various attributes agreeing with each couplet half.In accordance with couplet 28, Patrobini, the larva exhibits: 1, maxillary palpomere 2 longer and stouter than palpomere 3; 2, inner lobe, or lacinia of maxilla absent.In accord with couplet 29, Pterostichini, Drimostomina etc., it exhibits: 1, mandible with unisetose penicillus; 2, antennomere 2 shorter than 1 or 3; 3, nasale broadly and indistinctly produced.
The larval labium includes a bisetose ligula, with the setae LA1, LA2, LA3, LA4, and the ligular setal pair LA6 present, and the setae at position LA5 absent (Bous-quet and Larochelle 1984).The second pair of ligular setae-termed LA7 by Arndt (1998)-that are observed in Patrobini are not present.Also absent are the paired ligular pores homologized by Arndt with LA7.The configuration of bisetose ligula with pores substituting for LA7 is a synapomorphy for the subfamily Harpalinae (Arndt 1998).Thus the larval ligula deviates from Patrobini by the absence of LA7, but also deviates from members of subfamily Harpalinae by absence of two pores accompanying the LA6 setae on the ligula.In sum, the larva appears to represent a grade of development between Patobini and Harpalinae.The only candidates present in Tahiti that represent that phylogenetic level would be in the genus Mecyclothorax of the Moriomorphini.Corroborating this hypothesis, the larva shares characters with that of Melisodera picipennis Westwood, an Australian moriomorphine (Moore 1964).These characters include, among others: 1, a medially emarginated nasale; 2, cervical keel; 3, mandibular penicillus; 4, absence of a maxillary inner lobe; 5, bisetose ligula; 6, legs with two claws; and 7, urogomphi with short setose nodes.
The larva exhibits a 0.9 mm head width measured across the head capsule behind the stemmata, and a body length of 5.1 mm measured from the anterior margin of the nasale to the urogomphal tips (measurements made on a cleared larva).Based on these dimensions and the adult body length of 4.4 mm, the larva is considered to represent the third instar.
Given that M. poro was the only other Mecyclothorax species collected at this site, the larva is tentatively identified as that species based on geographic association.Of course, larval and adult individuals could have been deposited at this site during high water, but M. poro was not found at any other site suggesting this is its native habitat.Moreover, larvae and one adult of Metacolpodes eremita (Fairmaire) (Carabidae: Platynini) were also found together on moss-covered boulders at the lower entrance to the lava tube (Fig. 2A), suggesting that a resident streamside carabid community resides and breeds at this site.
Etymology.Among several meanings, the Tahitian word poro means corner or angle (Wahlroos 2002), and its use for the species epithet signifies the acute, projected hind pronotal angles characterizing this species.As Tahitian, the epithet is to be used as a noun in apposition.
Distribution and habitat.The adult and presumed larva of this species were collected at 705-725 m elevation, from moss and liverwort covered rocks along a stream running through a lava tube "tunnel"; the uncollapsed portion of a very large lava tube (Fig. 2A).This is the lowest elevation record for any Mecyclothorax species in Tahiti.For both the adult and larva, individuals were discovered through use of pyrethrin fog on the moss and liverworts, demonstrating that the individuals inhabited the depths of that vegetation.The rock face inhabited by the adult was wet, as the mouth of the lava tube was in shade for much of the day, and the site of adult collection was within a meter of the water's edge.The larva was found on a boulder in the middle of the streambed at the upper end of the lava tube where the moss was quite dry to the touch.

Discussion
The presence of seven precinctive Mecyclothorax species on Mont Mauru amply defines this isolated massif as a distinct area of endemism.All of the seven species from Mauru have putative adelphotaxa on one of the western mountains or, in one instance, possibly on the island of Moorea (Table 1).Thus corroborating Perrault's (1992, table 10.2) general findings, the presently known Mauru fauna has not diversified via autochthonous speciation within the massif, but instead has come about through more broadly based allopatric speciation implicating the various major massifs.
Mauru is isolated from the western mountains-Marau, Aorai, and Pihaaiatetaby the broad and deep Papenoo Valley.This present-day erosional depression within which the Papenoo River reaches the sea after having breached the Tahiti Nui caldera wall has been configured via successive phases of erosion, secondary volcanism, secondary erosion, and late-stage marine incursion.Secondary volcanic products emplaced within the valley are dated 440,000 years old (Becker et al. 1974).These flows and the original valley floor stood at 200-250 m elevation, an elevation that would fragment distributional ranges of all extant Mecyclothorax species.Thus it would appear that the Papenoo Valley has served as a formidable vicariant barrier between Mauru and the western mountains for at least 400,000 yr.Given the hypothesized species duration of 200-300 Kyr for Mecyclothorax species on West Maui (Liebherr 2011), the Papenoo Valley has been in place long enough to have facilitated allopatric speciation between the Mecyclothorax of Mauru and those of the various western mountains.Whether Mecyclothorax populations on Mauru have been isolated long enough from those on Mont Urufa to the south or Mont Aramaoro to the north, thereby allowing speciation to proceed among the isolated eastern massifs, must await biotic surveys of those peaks.
Discovery of seven Mecyclothorax species on Mauru elevates the number of Mecyclothorax described from Tahiti to 74 species (Perrault 1978a(Perrault , 1978b(Perrault , 1984(Perrault , 1986(Perrault , 1987(Perrault , 1988(Perrault , 1989)).This radiation is by far the most diverse species assemblage documented for Tahiti (Nishida 2008); a testament to the value of intense field work complemented by comprehensive revisionary taxonomy (Perrault 1992).That an assemblage of predatory insects should be the most speciose members of an isolated oceanic insect fauna may seem surprising at first glimpse.However such a result points to several aspects of community organization on such islands that make them fundamentally different from mainland communities.Firstly, botanical diversity is relatively low on isolated Pacific archipelagos (Mueller-Dombois and Fosberg 1998), removing the foundation for substantial diversification based on host plant specialization.Second, the predatory lifestyle ties the diversifying radiation to a relatively stable source of food comprising a taxonomically varied suite of food items, thereby lowering the risk of populations suffering extinction in any fragment of a primordial geographic range.Switching from a phytophagous to a predatory way of life is cited as one evolutionary attribute of island radiations (Gillespie and Roderick 2002).Experiencing enhanced survival as a ready-made predator in a disharmonic island fauna is more straightforward, not requiring an evolutionary change in life style.Climatic stability and geographic isolation characteristic of isolated oceanic islands conspire to select for reduced dispersal capability (Southwood 1977).In the instance of Mecyclothorax, this selected for vestigialization of metathoracic flight wings early in the radiation, with the end-result being 100% brachypterous taxa in the present-day Tahitian fauna.Moreover, given the holometabolous life cycle and small, terrestrially bound larvae of Mecyclothorax, long-distance dispersal does not occur in any life stage.Finally, Mecyclothorax species add small body size to this scenario, with individuals being able to reproduce within very limited ecological circumstances using minimal ecological resources.The seven new taxa that extablish Mont Mauru as a unique biogeographic entity were collected from habitats ranging 705-1110 m elevation.Yet the summit of Mauru stands at 1361 m elevation, begging the question of how much diversity remains to be discovered in the upper reaches of the mountain.An initial estimate of this undiscovered diversity can be made by comparing the elevationally limited samples from Mauru to those from the best sampled Tahitian mountain, Mont Marau (Fig. 1).Historically, Perrault (1992) based his taxonomic findings on 1388 specimens, 1103 from Tahiti Nui, of which over half-629-were collected on Marau.During the 2006 survey, 268 of the 539 specimens collected in Tahiti were found on Marau (unpubl.data).The aggregate Marau collections include 27 species, 21 of which were treated by Perrault (1992, table 10.2; M. muriauxioides Perrault will be synonymized in the future) and 6 more that remain to be described (unpubl.data).Of these species, 14 have been collected in habitats below 1100 m elevation, the elevational band sampled on Mauru that netted 7 species (Fig. 9).An additional 11 species have been collected on Marau from 1100-1360 m elevation, with two species known only from 1400 m near the summit of the mountain.Thus, assuming the faunas of these two mountains contain vicariant representatives of a primordial Tahiti Nui fauna, and that extinction associated with relative areal extent of the mountains or climatic differences associated with rainfall and aspect are not significant factors, we have sampled perhaps half of the Mauru Mecyclothorax fauna present below 1110 m elevation, and only a third to a fourth of the entire fauna on this massif.The only way to test this estimate is to redouble sampling efforts on the upper reaches of Mauru.Such findings will provide a baseline for characterizing the eastern Tahiti Nui fauna, allowing subsequent collections from neighboring massifs to answer questions about overall levels of diversity and speciation rates for the diverse Tahitian Mecyclothorax radiation.

Figure 1 .
Figure 1.Massifs of the Tahiti Nui and Tahiti Iti volcanos, Tahiti, Society Islands (redrawn and amended from Perrault, 1992).Massifs indicated were either sampled by Perrault (1978a et seq.) or during 2006 field work supporting the current study.Dashed lines indicate lowland valleys and associated headlands below 1000 m elevation that separate major massifs.

Figure 2 .
Figure 2. Habitats within which specimens of Mecyclothorax spp.were collected A Lava tube at 705 m elevation on Faatautia River drainage; holotype of Mecyclothorax poro collected by pyrethrin fogging vegetation growing on rocky bank between Dr. Curtis Ewing and climbing rope near edge of waterfall B Bank of Dicranopteris and Blechnum ferns at 1010 m elevation on Mont Mauru pylon trail; fern bank treated with pyrethrin fog by Dr. Dan Polhemus resulting in specimens of M. anaana and M. pirihao C Pyrethrin fog sheet apparatus around moss-covered Metrosideros trunk in low stature, open-canopy, wet rain forest at 1060-1110 m elevation, Mont Mauru, by which specimens of M. tihotii and M. putaputa were collected; trees did not exceed 4m height, mossmats were as thick as 15 cm

Figure 3 .
Figure 3. Mecyclothorax spp., dorsal view; small silhouette indicates actual size of beetle specimen at printed journal page size A M. tutei female holotype B M. tihotii male holotype C M. putaputa female paratype (CUIC)

Figure 4 .
Figure 4. Mecyclothorax spp., dorsal view; small silhouette indicates actual size of beetle specimen at printed journal page size A M. toretore female holotype B M. anaana male paratype (CUIC) C M. pirihao male paratype (CUIC) D M. poro female holotype

Figure 5 .
Figure 5. Male aedeagal median lobe and associated parameres, Mecyclothorax spp.; all figures to same scale A M. tihotii, right lateral view B M. tihotii, euventral view C M. anaana, right lateral view D M. pirihao, male dissection 1, right lateral view e M. pirihao, male dissection 2, right lateral view Abbreviations: fp flagellar plate lp left paramere of ostial flap rp right paramere vmf ventral microtrichial field.

Figure 8 .
Figure 8. Exposed gonocoxae and apical visible ventrite of Mecyclothorax holotype females, ventral view; four setae comprising median setal patch on female apical visible ventrite indicated by asterisks; number of apical fringe setae (afs) of basal gonocoxite 1 indicated in parentheses A M. tutei B M. putaputa C M. toretore
revised 19 species of the group, with Liebherr (2012) describing 2 more from Mont Tohiea, Moorea.